Fiber lasers are becoming an increasingly important option for LIDAR light sources in autonomous driving technology due to their operation in the eye safe 1550 nm spectral region and their intrinsic high beam quality, power and pulse characteristics. As an essential component for the pumping of fiber lasers, semiconductor laser diodes with high temperature stability, power and reliability are necessary. In this report we present the results of a continuous-wave (CW) single edge emitting laser diode designed to operate at 94x nm at 25 °C heat sink temperature and 97x nm at 100 °C. Various epitaxial and laser geometry designs have been implemented to optimize the laser performance over this wide environmental temperature range. The laser epitaxy is based on the AlGaAs/GaAs material system, with an InGaAs strained quantum well (QW). With various designs of laser geometry including emitting area and cavity length, devices are designed, grown, fabricated, and tested with the optimized design improving the temperature stability, power, and efficiency of the laser chip. A peak efficiency of over 54% at heat sink temperature of 105 °C and over 12 W before thermal roll-over occurs has been achieved. In addition to the thermal performance we also report the slow axis beam parameter product of the chip of <5 mm.mrad with polarization purity >98% at operating current and show the preliminary reliability data at the high temperature operation.
Fiber lasers are becoming dominant in the industrial metal cutting market up to 6kW levels due to their increasing performance delivered at aggressive price levels. A key force behind this is the availability of low-cost diode pump modules, consisting of combined single emitter laser chips. To further develop low pump cost an increase the reliable power available from each chip is required, and in principle this can be achieved by reducing facet power density, current density and lowering operational temperature by widening the emitter and increasing cavity length. Here we present the latest development of high-power laser diode chips at 976 nm wavelength designed for operation in 300W+ per pump module applications. For high power/high brightness applications we show a 150 μm contact opening, 5 mm cavity length chip delivering 20W at 20A CW at BPP of <5.5 mm.mrad. This laser has been deployed in several pump module product configurations from 155 W to 320 W with multi-cell module life test demonstrating over 20,000 hours at 90% survivability. For further power scaling we demonstrate design and performance of single emitter lasers with emitting facets of 220 μm to 300 μm. With 300 μm contact opening and 500 μm single emitter chip width 30W operation power is achieved at 32A with far field divergence less than 12°. Life testing is running at 46A with optical power of 41W for 2000 hours.
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